We are the creature that reflects on its own suffering. This is perhaps the only difference worth noting between us and the rest of the animal world.

We may continually mount expeditions toward understanding why pointless cruelty is visited on some but not others – or, to be more precise, why war not only exists but is endlessly reiterated – yet the question of arrival remains open. This everlasting search leads through particularly hellish territory in The Narrow Road to the Deep North. And when in the depths of the novel’s literal and figurative jungle we reach the heart of darkness, it is empty. The Australian author Richard Flanagan ("Gould's Book of Fish") has written not so much a fiction as a philosophical inquiry with characters; its strain is distinctly Nietzschean. After narrating what seems like every minute in the long life of one Dorrigo Evans, an officer and doctor who survived the insensible brutality that did in thousands of his fellow Australian POWs forced to build the so-called Death Railway from Bangkok through Burma in 1943, Flanagan hands us only one conclusion: nihilism in its purest essence. The story of Evans, his men, their agony, and the Japanese commanders who brought it on them offers a dizzying view onto “the terrible perfection of suffering and knowledge that made one fully human.”

It is a terrible thought, but one that also becomes beautiful in Flanagan’s meticulous working of it. His literary method is like an auger turning through rock and soil alike: patient, insistent, aiming for the buried core. From the beginning it’s clear we will be permitted ample time to witness all that befalls young men in war: packed off to their fates in sweatboxes of rail cars meant for freight. “They were men like other young men, unknown to themselves. So much that lay within them they were now travelling to meet.”

There are percipient lines like this imprinted, not only literally, on every page. Flanagan is a writer so profoundly observant that every other phrase manages to be compact and expansive at once. If this sounds like the definition of poetry, it should. The book is in nearly every aspect (including the compressed language) an epic in the classic formulation, that is, a long narrative retelling the heroic journey of an individual or group. The novel’s departures from the rules of the form are meant to serve its philosophical ends: Dorrigo Evans is not so much antihero as complicatedly flawed hero, proper to the book’s Dostoevskian drift. Thus he early on quotes not from Homer’s epic but from Tennyson’s darkly nuanced “Ulysses,” in which the journeyer is returned home, his quest in old age to somehow return to the past, even as it returns to him. And thus Flanagan makes Evans privately conflicted, a womanizer who questions the very possibility of love; a leader who is looked up to by his men, called the Big Fella even, but inwardly tormented by a fear that he is guilty of not having protected and saved more of them. (Of course, he faced only devil’s bargains in the camp, a thousand diseases besetting them from one side and overseers with a supreme grasp of sadism from the other, men dying like flies from lack of food and medicine.) He carries through all his years the suspicion that a brilliant catch in high school rugby might have been the apex of his life.

The horrific suffering of the prisoners is almost lovingly rendered, from the graphic effects of dysentery to the unhinged behavior of a guard known as the Goanna, and whether Flanagan spoons it on a bit thick or if he has merely represented the truth no one but a survivor could say. The story of the rail line built to supply the Japanese army massed in Burma, at an unspeakable cost in human lives, was the basis of David Lean’s great film "The Bridge on the River Kwai," itself based on a fictional account by prisoner Pierre Boulle. One of several themes here is the “indomitable Japanese spirit” that the camp commanders (in somewhat unconvincing internal monologues) use to reassure themselves of their righteousness. This is the sort of nationalist propaganda from which all prisons are made, the cover story for brutality beyond imagining.

And poetry underwrites it all. This book is saturated by it, as well as made from it. The characters think about it – in bed with a lover, before decapitating someone with a sword – while the author deploys it in layered ways. Kipling’s “Lest we forget – lest we forget!” keens the theme of remembrance as final justice. The protagonist’s character is illuminated by means of his taste for the conservative canon, including Browning. The novel’s title comes from Bashō, Japan’s great haiku master of the 17th century, and finely wrought exemplars of the form tipped in throughout make for an elegant gallery. Artistry in the midst of suffering; artistry out of suffering.

Flanagan poses big questions with such stealth we seem to come upon them in our own thoughts by surprise. And so we are jolted to realize how easily we had accepted the convention of the lover of poetry as gentle and perceptive, morally superior. In a feat of literary inventiveness, Flanagan uses an appreciation for haiku as a psychic bridge between ostensibly opposed natures; both the cruel captors and their chief prisoner are sensitive to its high-tensile beauty. In so doing the author asks if they can then truly be mortal enemies, or if in a mirror world the beaten captive would exact revenge as inhuman as he once received.

"The Narrow Road to the Deep North" is many things at once. An epic that negates itself. A war story and also (by, yes, convention) a love story: this is how we more deeply appreciate the suffering of soldiers, when we have previously seen them expressing tender affection. It is not perfect, though it has received a berth on the longlist for the Man Booker Prize. (Rhetorical excess mars two climactic scenes and, more unforgivably, makes of a villain an archetypal villain; archetypes are death to fiction.) But it dares the big revelation. What people do to one another, good and bad, “just is.” There is no reason. There’s no cause, no blame, and above all no understanding. They make love, they brutalize. All of it is inexplicable. Nihil est, Flanagan says. And that’s not nothing.